Insulin secreting and α-glucosidase inhibitory activity of Coscinium fenestratum and postprandial hyperglycemia in normal and diabetic rats.

Abstract

This work focused on the effect of Coscinium fenestratum ethanolic extract on plasma glucose concentrations in normal and streptozotocin (STZ)-induced diabetic rats, the stimulatory effect on insulin secretion from perfused rat pancreas and the inhibitory effects on rat intestinal α-glucosidase enzymes, maltase and sucrase. In oral glucose, maltose and sucrose loading tests, the extract (250 - 1,000 mg/kg) significantly decreased plasma glucose concentrations in a dose-dependent manner. The extract (1,000 mg/kg) was most effective in decreasing plasma glucose concentrations and the response was closed to those of glibenclamide (5 mg/kg) and acarbose (3 mg/kg). In perfused rat pancreas, the extract (10 µg/ml) stimulated insulin secretion in a biphasic pattern. However, the berberine at the same dose as the extract slightly increased insulin secretion by 1.33-fold over the basal control group. In addition, the extract inhibited the activities of both maltase and sucrase with the IC50 of 3.89 and 11.22 mg/ml, respectively. Our findings suggest that the C. fenestratum ethanolic extract exerted anti-hyperglycemic activity by stimulating insulin secretion and a-glucosidase inhibition. Key words: Coscinium fenestratum, streptozotocin, a-glucosidase, insulin secretion, perfused rat pancreas.